The level, presence, and/or absence of glucose in a subject can have a number of consequences. For example, fluctuations of blood glucose levels can result in one of two physiological states, hypoglycemia and hyperglycemia. Hypoglycemia is defined as plasma glucose levels below normal. Hypoglycemia can be symptomatic or asymptomatic. For example, subjects suffering from postprandial hypoglycemia generally have symptoms of adrenergic stimulation including diaphoresis, anxiety, irritability, palpitations, tremor, and hunger. Such symptoms typically occur from about 2 to 4 hours postprandially and tend to occur suddenly with symptoms generally subsiding in about 15 to 20 minutes. Hypoglycemia can be caused by release of adrenergic and cholinergic hormones. Postprandial hypoglycemia is often idiopathic, however, it can be caused by early diabetes, alcohol intake, renal failure, and drug treatments. In addition, a category of hypoglycemia exists which is designated as fasting hypoglycemia. Clinically, this form of hypoglycemia may have symptoms of neuroglycopenia including headache, fatigue, and mental dullness. In more severe cases, hypoglycemia can progress to confusion, blurring of vision, seizure, and ultimately loss of consciousness or seizure. Fasting hypoglycemia can occur with a fast of greater than 4 hours, and further can be caused by insulinoma (resulting from self-administered insulin or intake of other hypoglycemic agents, alcohol abuse, liver disease (e.g., decreased gluconeogenesis), pituitary insufficiency, or adrenal insufficiency).
Hyperglycemia, on the other hand, refers to excessive levels of blood glucose in a subject. There are many forms of hyperglycemia, the primary form being diabetes mellitus (DM) which is defined as hyperglycemia secondary to decreased insulin production or an increase in peripheral tissue resistance to the action of insulin. There are several classifications of DM including, type 1 DM, type 2 DM, gestational DM, and secondary DM (which can, for example, be the result of a variety of drug therapies, disease states (e.g., pancreatitis, Cushing's syndrome), trauma, surgery, and others causes). Further, in the case of severe insulin deficiency, a starvation-like state develops resulting in acidosis (typically referred to as diabetic ketoacidosis). Symptoms of ketoacidosis can include rapid respiration, acetone breath, vomiting, dehydration, nausea, abdominal pain and changes in mental stability.
Thus, there is a need for frequent monitoring of glucose levels in many subjects who are at risk for hypogylcemia and hyperglycemia.